The objective of this study is to determine if the absence of apartic acid at position 57 of the HLA-DObeta chain and presence of arginine at position 52 of the HLA-DOalpha chain is as strong of a genetic marker in African Americans for IDDM as it is in Caucasians. There appears to be a 5-fold difference in IDDM risk among African Americans residing in various areas of the U.S. The variations seen may be due to the presence or absence of these genetic markers which may be related to the degree of Caucasian admixture in African Americans across the U.S. It is important to establish a population-based diabetes registry to characterized the genetic susceptibility of IDDM as it relates to HLA alleles. Washington, D.C. provides an unique opportunity to examine incidence data and genetic risk factors associated with IDDM in African Americans because of the large percentage of them residing in the area. With an understanding of the genetic risks of IDDM in African Americans, preventive strategies can be more effectively implemented. The specific aims of this project are to: (1) determine the incidence of IDDM from 1990 to 1999 among African American children les than the age of 15 years from Washington, D.C., (2) determine the degree to which the molecular polymorphisms of HLA class II genes are associated with IDDM susceptibility among African Americans from Washington, D.C., (3) evaluate the genotype-specific IDDM incidence rates associated with HLA class II susceptibility genes, and (4) compare the genotype distributions and the genotype specific IDDM incidence rates among African Americans from Washington, D.C. with established registries in the U.S.